This invention relates to a method and apparatus for automatically making a so-called "bag-in-carton" which is a container having a bag therein.
A bag-in-carton, which is a combination of a paperboard carton and a bag made of plastic, metal foil or the like, has been used as a container for products which need air tight packing or for some kinds of liquid.
A typical method for making such bag-in-carton comprises cutting a tube of bag material to provide a length of the tube, sealing one end of the length of the tube to form a bag, folding a flat carton blank which is punched out from a sheet of paper board so as to enclose the bag therein and forming a rectangular paper tube and adhering the bag to the carton blank. During the above folding step, upper and lower end flaps of the blank are not folded. The obtained rectangular tubes are collapsed and then stored flat. When the flattened carton tubes are used, the tubes are set up into a rectangular form and the bags therein which are bonded to the carton tubes are concomitantly opened. Then, the flaps of the end of each of the carton tubes adjacent the sealed end of the bag therein are folded and bonded to each other to close the end, and then the carton with one end closed is fed to a product loading machine.
According to such a method, the rectangular carton tubes are stored flat for a long time. Thus, if the material of the bags in the carton tubes is apt to cause blocking or sticking, the carton tubes are not easily set up when they are going to be used. Furthermore, at least a portion of the bag is fixed to the carton. Therefore, forces applied from outside of the product loaded carton, for example during transportation thereof, tend to be directly transmitted to the interior of the bag thereby causing a problem of damage to the products in the bag. Furthermore, when the process for combining the carton and the bag is effected automatically, it is necessary to accurately synchronize the feeding of the carton blanks with that of the bags and to make constant the orientations of the cartons and the bags. For so dealing with bags, it is necessary that the bags have certain stiffness.
Another typical method comprises putting a sheet of bag material around a mandrel, heat sealing the side seam and the bottom portion of the bag material to form a bag, and putting a carton blank around the bag and bonding the bag and carton at certain places or throughout. In this method, too, problems arise unless the bag material has certain stiffness; for example, the bag material curls or does not conform to the mandrel. Furthermore, this method is also accompanied with the problem of damage to the packed products during transportation as in the first method, since bonding between the bag and carton is necessary.
Mechanisms and the process used in the abovementioned two methods for bonding bags to cartons are complicated and time consuming. Thus, they significantly increase the cost of completed packages.
Another typical method comprises separately preparing a bag and a carton, putting products in the bag and thereafter inserting the loaded bag in the carton. According to this method, the possibility of damage to the products during transportation decreases since the bag is not fixed to the carton. It has been experimentally proven there is less damage to the products when the bag is not fixed to a carton than when the bag is fixed to the carton. Thus, the bag-in-carton made by the third mentioned method is suitable for containing snacks such as biscuits and potato chips. However, the loaded bag is not evenly shaped. Usually, the lower portion of the loaded bag tends to become larger than the upper portion. Thus, if the loaded bag is to be inserted in a carton having a size closely corresponding to that of the bag, it is necessary to manually reform the loaded bag to an appropriate shape. Or, if the loaded bag is to be inserted automatically in a carton, it is necessary that the carton be much larger than the bag thereby increasing the cost and provoking complaints from consumers.